Method and apparatus for depositing films

ABSTRACT

In a sputtering apparatus, target particles to be deposited onto a substrate are selectively ionized relative to other particles in the deposition chamber. For example, titanium or titanium-containing target particles are selectively ionized, while inert particles, such as argon atoms, remain substantially unaffected. Advantageously, one or more optical ionizers, such as lasers, are used to create one or more ionization zones within the deposition chamber in which such selective ionization takes place.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/384,470, filed Aug. 27, 1999 now U.S. Pat. 6,752,912, which is acontinuation-in-part of U.S. application Ser. No. 08/631,465, field Apr.12, 1996 now U.S. Pat. 6,827,824.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of integratedcircuit manufacturing technology and, more particularly, to a method fordepositing selected target atoms.

2. Background of the Related Art

This section is intended to introduce the reader to various aspects ofart which may be related to various aspects of the present inventionwhich are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

In the manufacturing of integrated circuits, numerous microelectroniccircuits are simultaneously manufactured on semiconductor substrates.These substrates are usually referred to as wafers. A typical wafer iscomprised of a number of different regions, known as die regions. Whenfabrication is complete, the wafer is cut along these die regions toform individual die. Each die contains at least one microelectroniccircuit, which is typically packaged and combined with other circuits toform a desired electronic device, such as a computer. Examples ofmicroelectronic circuits which can be fabricated in this way include amicroprocessor and a memory, such as a dynamic random access memory(“DRAM”).

Although referred to as semiconductor devices, integrated circuits arein fact fabricated from numerous materials of varying electricalproperties. These materials include insulators or dielectrics, such assilicon dioxide, and conductors, such as aluminum or tungsten, inaddition to semiconductors, such as silicon and germanium. These variousmaterials are fabricated and arranged on the wafer to form electricalcircuits.

For instance, in the manufacture of integrated circuits, conductivepaths are formed to connect different circuit elements that have beenfabricated within a die. Such connections are typically formed withinstructures, such as trenches or holes. For example, conductive lines maybe fabricated by depositing conductive material within trenches, andcontacts or interconnections may be fabricated by depositing conductivematerial within openings in intermediate insulative layers. Theseopenings are typically referred to as “contact openings” or “vias.” Acontact opening is usually created to expose an active region, commonlyreferred to as a doped region, while vias traditionally refer to anyconductive path between any two or more layers in a semiconductordevice.

After a contact opening, for instance, has been formed to expose anactive region of the semiconductor substrate, an enhanced doping may beperformed through the opening to create a localized region of increasedcarrier density within the bulk substrate. This enhanced region providesa better electrical connection with the conductive material which issubsequently deposited within the opening. One method of increasingconductivity further involves the deposition of a thintitanium-containing film, such as titanium silicide, over the wafer sothat it covers the enhanced region at the bottom of the contact openingprior to deposition of the conductive layer. Once the bottom of thecontact opening has been lined with a thin titanium-containing film, itis usually desirable to fill the contact opening with a conductivematerial, such as titanium, to complete the formation of the contact.

Of course, it should also be noted that thin films oftitanium-containing compounds find other uses as well in the fabricationof integrated circuits. For example, titanium nitride is used as adiffusion barrier to prevent chemical attack of the substrate, as wellas to provide a good adhesive surface for the subsequent deposition oftungsten. Indeed, many reasons exist for depositing thin films betweenadjacent layers in a semiconductor device. For example, thin films maybe used to prevent interdiffusion between adjacent layers or to increaseadhesion between adjacent layers. Titanium nitride, titanium silicide,and metallic titanium are known in the art as materials that can bedeposited as thin films to facilitate adhesion and to reduceinterdiffusion between the layers of a semiconductor device. Other filmsthat may be useful for these purposes also include titanium tungsten,tantalum nitride, and the ternary alloy composed of titanium, aluminum,and nitrogen.

The deposition of titanium and titanium-containing material is just oneexample of a step in the manufacture of semiconductor wafers. Indeed,any number of thin films, insulators, semiconductors, and conductors maybe deposited onto a wafer to fabricate an integrated circuit. As thesize of the microelectronic circuits, and therefore the size of dieregions, decreases, the percentage of reliable circuits produced on anyone wafer becomes highly dependent on the ability to deposit these thinfilms uniformly at the bottom of the trenches and contact openings andto fill the trenches and contact openings with conductive material.

Integrated circuit technology has advanced through continuingimprovements in photolithographic processing so that smaller and smallerfeatures can be patterned onto the surface of a substrate. These smallerfeatures not only make the resulting electronic circuits more compact,but they also make the circuits operate at a higher speed. However, ascontact structures, such as trenches, contact openings, and vias, aremade smaller, they become more difficult to fill.

To begin to appreciate this problem, it should be understood that thelateral dimension of such structures is typically referred to as the“width” and the vertical dimension of such structures is typicallyreferred to as the “depth.” The aspect ratio is the ratio of depth towidth. Thus, as the features have become smaller, the aspect ratio hasrisen, resulting in high aspect structures. As discussed above, thesehigh aspect ratio structures usually must be filled with an appropriatematerial before continued processing. Most often the objective is toprovide void-free, and preferably seam-free, filling of such structures.Indeed, many different techniques have been developed in an effort toaddress this problem. For example, films may be deposited by severaldifferent methods, such as spin-on deposition, chemical vapor deposition(CVD), plasma enhanced chemical vapor deposition (PECVD), and physicaldeposition.

In spin-on deposition, the material to be deposited is mixed with asuitable solvent and spun onto the substrate. The primary disadvantageof spin-on deposition is that nominal uniformity can only be achieved atrelatively high thicknesses. Furthermore, this technique often covershigh aspect ratio structures without filling them, thus resulting invoids. Therefore, this method is primarily used for the deposition ofphotoresist and the like, and it is generally not useful for thedeposition of thin films or the filling of high aspect ratio structures.

Of the methods mentioned above, it is arguable that CVD and PECVD arebest suited to deposit the thinnest films. However, films deposited inthis manner tend to exhibit relatively conformal deposition on slantedor vertical surfaces as well as on the bottom surfaces of the trenchesand contact openings. While such conformal deposition of thin filmscertainly finds many uses in the fabrication of integrated circuits, ittends to be somewhat problematic when the goal of a particular processstep is to deposit a thin film only at the bottom of a structure or tofill a high aspect ratio structure. Because most deposition techniquesof this type inherently deposit material on the sidewalls at the samerate as at the bottom of a contact structure, the sidewall depositiontends to close off the opening of the structure before the structure iscompletely filled. When the structure is closed off in this manner, avoid exists within the structure and a seam exists at the opening. Voidsare undesirable in a contact structure because air does not conductelectricity well, and seams are undesirable because solvents and thelike which tend to accumulate in the seams can degrade the contact.Thus, chemical vapor deposition techniques are generally onlysuccessfully used for moderate aspect ratio structures where sidewalldeposition does not close off the structure before it is filled.

In sputter deposition, the material to be deposited, typically referredto as the target, is bombarded with positive inert ions. Once thematerial exceeds its heat of sublimation, target atoms are ejected intothe gas phase where they are subsequently deposited onto the substrate.Sputter deposition has been widely used in integrated circuit processesto deposit titanium-containing films. However, the primary disadvantageof sputter deposition is that high aspect ratio structures are difficultto fill due to “shadowing” effects. Shadowing effects are produced dueto the fact that the sputtered particles tend to travel in random oruncontrolled directions, i.e., isotropically, and thus strike thesidewalls of the contact structure at an angle. The particles thereforeare deposited on the sidewalls, causing a film growth on the sidewalls.The sidewall film growth eventually closes off the via before it isfilled. This problem is often acute in the case of multi-layer metal(MLM) designs where high aspect ratio vias are etched into a dielectriclayer and metal must be deposited to fill the via.

To fill a contact structure, it is desirable to deposit films that formpreferentially at the bottom of the structure rather than on thesidewalls. Thus, physical deposition techniques, such as sputtering,which produce isotropically traveling particles were traditionallylimited for use in filling low aspect ratio structures. However, varioustechniques for directing sputtered target atoms toward the wafer havebeen developed in efforts to address the problem of isotropicallytraveling particles collecting on the sidewalls of the contactstructure. For example, collimators have been employed to preventrandomly directed atoms from reaching the surface of the wafer. Incollimated sputtering, lattice-shaped collimators block particlestraveling towards the wafer at unacceptable angles. Such collimatorstypically have high aspect ratio tunnels that allow only particleshaving acceptable trajectories to pass through. The remaining particlesimpact and deposit on the sidewalls of the collimator, rather than onthe sidewalls of the contact structures on the wafer. However, sincefewer than 50% of the sputtered particles tend to travel in the shadowangle of 90°+/−5°, most of the particles deposit onto the collimatorrather than on the wafer. Thus, while collimators prevent much of theundesirable build up of particles on the sidewalls of contactstructures, they do so at the expense of low deposition rates and a highdegree of particulate contamination from the material deposited on thecollimator sidewalls. Moreover, collimators provide limiteddirectionality, as the particles leaving the collimator still. typicallyhave ±5° variation in their trajectories.

In an effort to improve the deposition rate of collimated sputtering,the wafers have been electrically charged to attract charged titaniumions, and complex induction coils have been used to create a magneticfield to enhance the life time of titanium ions. Because thesetechniques cause the titanium ions to travel in a directionsubstantially perpendicular to the wafer, they increase the number ofsputtered particles that will pass through the collimator for depositionon the wafer. However, these techniques affect all particles in asimilar manner. In other words, the charged wafer attracts all ions, notjust titanium ions, and the magnetic field enhances the life time of allions, not just titanium ions. Thus, these techniques will ionize argonparticles as well, which bombard and damage the wafer.

The present invention may address one or more of the problems set forthabove.

SUMMARY OF THE INVENTION

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms the invention might take and that these aspects are notintended to limit the scope of the invention. Indeed, the invention mayencompass a variety of aspects that may not be set forth below.

In accordance with one aspect of the present invention, there isprovided an apparatus for depositing film. The apparatus includes adeposition chamber being to hold inert particles and target particles.An ionizer creates an ionization zone within the deposition chamber. Theionizer ionizes the target particles passing through the ionization zonewhile leaving the inert particles substantially unaffected.

In accordance another aspect of the present invention, there is provideda method for depositing a film onto a substrate. The method includes theacts of: passing target particles and inert particles through anionization zone in a deposition chamber to ionize the target particleswhile leaving the inert particles substantially unaffected; and steeringthe ionized target particles into a collimated stream directed along agiven path toward the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 illustrates a schematic view of a first embodiment of adeposition apparatus in accordance with the present invention;

FIG. 2 illustrates a top plan view of the deposition apparatus of FIG.1;

FIG. 3 illustrates a schematic view of a second embodiment of adeposition apparatus in accordance with the present invention;

FIG. 4 illustrates a schematic view of a third embodiment of adeposition apparatus in accordance with the present invention;

FIG. 5 illustrates a schematic side view of the electrostatic collimatorillustrated in FIG. 4;

FIG. 6 illustrates a schematic cross-sectional view of the electrostaticcollimator illustrated in FIG. 5;

FIG. 7 illustrates a schematic view of a fourth embodiment of adeposition apparatus in accordance with the present invention;

FIG. 8 illustrates a schematic view of a fifth embodiment of adeposition apparatus in accordance with the present invention;

FIG. 9 illustrates a semiconductor wafer and its constituent dieregions;

FIG. 10 illustrates a diagrammatic cross-section of a semiconductorwafer processed in accordance with the present invention, wherein a thinfilm has been deposited onto the surface of a die including the bottomof a contact opening;

FIG. 11 illustrates a diagrammatic cross-section of a semiconductorwafer processed in accordance with the present invention, wherein aconductive layer has been deposited over the thin film to fill thecontact opening partially; and

FIG. 12 illustrates a diagrammatic cross-section of a semiconductorwafer processed in accordance with the present invention, wherein aconductive layer has been deposited over the thin film to fill thecontact opening completely.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the interest of clarity, not all features of an actual implementationof an integrated circuit process are described in this specification.This illustration is restricted to those aspects of an integratedcircuit process involving the sputter deposition of material, such astitanium and titanium containing films. Conventional details ofintegrated circuit processes, such as mask generation, resist casting,resist development, etching, doping, cleaning, implantation andannealing are not presented as such details are well known in the art ofintegrated circuit manufacture.

The methods and apparatus disclosed herein provide collimated streams ofparticles for film deposition. The particular embodiments are describedwith reference to a sputtering apparatus, but it should be readilyapparent that other film deposition techniques, such as evaporation,E-gun, and CVD, might be adapted in accordance with these teachings.

In the specific examples described below, the sputtering apparatusdeposits a metal or a metal-containing film onto the surface of asemiconductor wafer. While this is a common and useful application, itshould be understood that the teachings may also apply to the depositionof other types of materials, such as dielectrics, semiconductors, andthe like.

As mentioned above, one problem depositing materials using sputtering isthat particles typically have an isotropic distribution of trajectorieswhen they are removed or extracted from a source, also called a target.In other words, the particles move away from the target according to arelatively random distribution of trajectories. To provide a collimatedstream, the particles must be given longitudinal energy so that theytravel straight toward the substrate, or the particles must be otherwisedirected toward the substrate.

As described below with reference to the illustrated embodiments,selected particles within the deposition chamber are redirected andgiven longitudinal energy to create the collimated streams. The severalembodiments shown and described herein illustrate various manners inwhich the basic teachings may be used to enhance sputtering techniques.Other modifications may be apparent to those skilled in the art and maybe considered equivalent to the embodiments shown and described herein.

Turning now to the drawings, and referring initially to FIG. 1, whichillustrates a first embodiment of a sputtering apparatus generallydesignated by the reference numeral 10. The apparatus 10 is shown as asingle wafer sputter deposition apparatus. However, the teachings may bereadily applied to a multiple wafer sputtering apparatus as well. Asubstrate 12, such as a semiconductor wafer that may include one or moresurface layers and patterned features formed thereon, rests on a support14 at one end of the deposition chamber 15. A target 16, which includesatoms to be deposited onto the substrate 12, is provided at an oppositeend of the deposition chamber 15. Process gasses are supplied via a port18 and fill the space between the target 16 and the substrate 12.Ordinarily, the apparatus 10 is maintained at a low pressure by a vacuumpump (not shown) coupled to an outlet port 20.

A high frequency or microwave energy source 22 may be coupled to thedepositon chamber 15 via a wave guide 24 to supply high frequency energyinto a region 26 near the target 16. The application of high frequencyenergy from the source 22 causes a plasma to be generated in the region26 by electron cyclotron residence (ECR) heating. The plasma istypically comprised of the process gasses that are ionized by the ECRheating to a very high energy state giving individual ions in the plasmasignificant kinetic energy. Process gasses provided through the port 18typically include an inert gas such as argon. However, in a reactivesputtering or CVD system, process gasses would include inert gassesalong with components that would react with the materials sputtered fromtarget 16 to create films that deposit on the substrate 12.

The excited argon atoms in plasma strike the surface of the target 16with energy sufficient to cause atoms on the surface of the target 16 tobe ejected into the plasma. Some of the atoms ejected from the target 16have sufficient energy to travel through the low-pressure environment tothe substrate 12 where they deposit to form a film. Other ejected atomshave insufficient energy and are ionized in the plasma. These atoms areoften attracted back to the target 16 by a negative bias applied to thetarget 16 by a voltage supply 28. These atoms return to the target 16and re-sputter additional atoms from the target 16.

A voltage supply 30 is coupled to the support 14 to provide a largenegative bias to the substrate 12 during the sputter deposition. Thisnegative bias creates an electric field between the substrate 12 and theplasma that tends to attract positive ions from the plasma toward thesubstrate 12. The DC field created by the voltage source 30 only actsupon ionized atoms from the target 16 which at any point in timerepresent only a portion of the atoms ejected from the target 16. Theionized target atoms in the plasma are thus given some degree ofdirectionality by the bias supply 30 to improve the properties of thedeposited film.

However, because the field created by the bias supply 30 only affectsionized target atoms, the improvement in directionality is limited. Thisis particularly true in the case of metal target particles whichrecombine quickly as they leave the plasma to form neutral metalparticles. Once neutralized, the neutral target atoms in a sputterapparatus are not affected by static electric or magnetic fields and,thus, continue on their original random trajectory. Thus, an importantfeature of the apparatus 10 is the introduction of a secondary ionizer32.

The secondary ionizer 32 creates a secondary ionization zone between theplasma in the region 26 and the surface of the substrate 12. Thesecondary ionizer 32 re-ionizes the target atoms thus allowing them tobe accelerated and steered using static electric and/or magnetic fields.In the embodiment shown in FIG. 1, the secondary ionizer 32advantageously supplies its optical energy through quartz windows 34 inthe side of the deposition chamber 15. The static electric field createdby the supply 30 will accelerate the ionized target atoms in a directionsubstantially perpendicular to the surface of the substrate 12 once thetarget atoms have passed through the secondary ionization zone.

The secondary ionizer 32 provides optical energy having sufficient powerand a selected wavelength to ionize selected target atoms or moleculeswithout substantially ionizing unwanted atoms or molecules. In thisexample, using a titanium target in an inert argon gas, the opticalenergy advantageously selectively ionizes the titanium atoms withoutionizing the argon atoms. Of course, in a reactive sputtering system,the optical energy would advantageously ionize the titanium-containingmolecules without ionizing other atoms or molecules. For titanium, thefirst ionization energy is 658.8 KJ/mol or 6.83 eV, and the equivalentwavelength of electromagnetic waves for this energy is about 177 nm. Toprovide this type of selective ionization of titanium atoms, thesecondary ionizer 32 may be, for example, a F₂ excimer laser having awavelength of approximately 157 nm. As another example, an extreme UV(EUV) laser with recycling Xe having a wavelength of 13.4 nm may beused.

To describe the operation of the secondary ionizer 32 in further detail,FIG. 2 illustrates a top plan view of the first embodiment. Thesecondary ionizer 32 advantageously causes the optical energy tointeract with a significant number of target atoms in the secondaryionization zone. One method of accomplishing this task is to distributea plurality of optical sources 60 about the periphery of the depositionchamber 62. The quartz windows 34 allow the optical energy from thesources 60 to enter the deposition chamber 62. Advantageously, amirrored inner surface 64 is provided in alignment with the path of theoptical energy from the sources 60. The mirrored inner surface 64 causesthe optical energy to reflect multiple times within the depositionchamber 62 creating a plane of optical energy which interactscontinuously with target atoms that intersect the plane of opticalenergy.

As discussed above, the sources 60 are lasers having a wavelength chosento ionize the target particles, while leaving other particles relativelyunaffected. Suitable lasers may include excimer lasers, tuned dyelasers, or other optical energy sources capable of supplying sufficientpower at a desirable wavelength into the deposition chamber 62.Alternatively, the sources 60 may be ultraviolet or visible lightsources focused with conventional lenses (not shown) to fill thesecondary ionization zones with optical energy. The sources 60 mayoperate continuously or in pulses depending on the equipment selected.

Although a mirrored inner surface 64 is illustrated in FIG. 2, it ispossible to form the quartz windows 34 as lenses which will bend theoptical energy from the sources 60 into a plane as it enters thedeposition chamber 62. Various optical techniques that create sufficientinteraction and spread light from the sources 60 sufficiently to createan ionization zone within the deposition chamber 62 may also beadequate.

In this first embodiment shown in FIG. 1, a collimated stream isproduced by re-ionizing the target atoms in a region between the plasmaand the substrate 12, so that the DC field can accelerate the re-ionizedtarget atoms created by secondary ionizer 32 in a directionperpendicular to the surface of substrate 12. However, the longer atarget atom can be kept ionized the greater steering capability isprovided. Thus, as second embodiment of a sputtering apparatus 36 isillustrated in FIG. 3 as having multiple levels of secondary ionizers.To prevent confusion, elements in FIG. 3 that are analogous to elementsin FIG. 1 are identified with identical reference numerals and may beconsidered to operate in the manner described above.

In regard to the multiple levels of secondary ionization, FIG. 3illustrates two secondary ionizers 32A and 32B which are provided toincrease the amount of time that each target atom remains ionized. Asthe plasma in the region 26 extracts target particles from the target12, they may or may not be initially ionized in plasma as describedabove. Atoms having sufficient momentum pass out of plasma withnon-collimated or isotropic trajectories. The first secondary ionizer32A operating through the window 34A ionizes the target atoms as theyintersect the path of ionizer's tuned optical energy. These selectivelyionized target atoms are accelerated in a direction perpendicular to thesubstrate 12 by the DC field created by bias supply 30, while theunselected atoms remain neutral and unaffected by the DC field. Toensure that the target atoms remain ionized so that the DC field cancontinue to accelerate them in a collimated stream toward the substrate12, the target atoms are once again ionized by the secondary ionizer 32Boperating through the window 34B. Once the target atoms are selectivelyionized again, the DC field created by bias supply 30 can furtheraccelerate and provide greater lateral momentum to the target atoms.

Although two secondary ionizers 32A and 32B are shown in FIG. 3, itshould be understood that any suitable number of secondary ionizers maybe provided in a practical apparatus. Due to the relatively shortlifetime of metal ions, it is believed that several levels of secondaryionization in the travel path between the plasma and the substrate 12may be appropriate and desirable to provide improved directionality toparticles. The remaining embodiments described below do not showmultiple secondary ionizers, however it should be understood thatmultiple secondary ionizers may be incorporated with any of thevariations described below.

FIG. 4 illustrates a third embodiment of a sputtering apparatus 38.Again, to prevent confusion, elements in FIG. 4 that are analogous toelements in FIG. 1 are identified with identical reference numerals andmay be considered to operate in the manner described above. In theembodiments shown in FIGS. 1 and 3, collimation was provided by a DCfield created between the plasma and the substrate 12. As discussedabove, lattice-shaped collimator structures are known and used inconnection with sputtering devices to improve collimation of particlestreams. Of course, such collimators are mechanical devices thatphysically block particles having unacceptable trajectories. Thisphysical blocking typically results in reduced deposition rate andparticulate contamination within the sputter chamber.

Although a conventional lattice-type collimator may be used,particularly if the deposited atoms are steered to minimize depositionon the collimator, the embodiment shown in FIG. 4 advantageously employsan electrostatic collimator 40 instead. The electrostatic collimator 40includes grids 42 and 44 that are differentially charged to oppositepolarities by respective power supplies 46 and 48. Voltage outputs ofthe power supplies 46 and 48 are set to attract and accelerate targetions as they move through the collimator 40 in a manner that focusestheir trajectories toward the substrate 12.

The electrostatic collimator 40 may be formed as a mesh, screen, or asheet of conductive material having holes of any size or shape formedtherein. Advantageously, the openings in the electrostatic collimator 40are large compared to the surface area that is blocked by electrostaticcollimator 40. Given such a structure, most of the ionized atoms willtend to pass through the electrostatic collimator 40 except for a smallpercentage of atoms that deposit on collimator 40.

Alternatively, a conventional lattice-type collimating structure can beprovided using a conductive material. The lattice-type structureprovided may exhibit the advantages of a conventional collimator in thata high degree of collimation is provided by the high aspect ratio of theopenings. However, to the extent that the random trajectories of thetarget atoms have not been redirected towards the substrate 12 by thesecondary ionizer 32, the conventional lattice-type collimator will tendto accumulate more target atoms than the electrostatic collimator 40.Specifically, by coupling a charge to the electrostatic grid collimator40, the ionized target particles are steered through the collimator 40rather than simply blocked as with a lattice-type collimator. Thisresults in a higher degree of material passing through the electrostaticcollimator 40 to provide improved deposition rates and reducedparticulate deposition on the collimator.

FIGS. 5 and 6 illustrate details of the electrostatic collimator 40.FIG. 6 shows a cross-sectional view of the collimator 40 takenorthogonally from the view shown in FIG. 5. Field lines illustrated bythe dashed circles in FIG. 6 represent equipotential surfaces in theelectrostatic field created by the voltage supplied to electrostaticcollimator grids 42 and 44 by the voltage supplies 46 and 48. It shouldbe understood that the equipotential surfaces shown in FIG. 6 aregreatly simplified yet are suitable for the purposes of thisdescription. The actual field shapes will be more complex due tointeraction between the grids 42 and 44.

In the case of accelerating positive target ions, a negative highvoltage, typically in the range of 500 to 5000 volts DC, is supplied bythe voltage supply 48 and applied to the grid 44. This acts to attractthe positive ions toward the grid 44 with high velocity. A relativelylow negative voltage, typically in the range of 50 to 500 volts DC, issupplied by the voltage supply 46 simultaneously to the grid 42. Thepositive ions do not respond to the voltage on the grid 42 until theyhave already been drawn very near to the grid 42 by the higher negativevoltage applied to the grid 44. As positive ions near the grid 42, thepositive ions are repulsed and deflected toward a center axis betweenthe adjacent elements of the grid 42. This deflection effectively steersthe ions through the collimator 40 and prevents the ions from physicalcontact with and deposition on grids 42 and 44. In essence, the grid 42focuses the ions and the grid 44 accelerates the ions toward thesubstrate 12. The velocity and directionality is achieved by fine tuningthe relative voltages between applied to the grids 42 and 44, and theshape and design of the holes in the grids 42 and 44 may also be variedto increase ion flux and/or increase the ion focusing properties.

While the electrostatic grid collimator 40 is described in conjunctionwith secondary ionization, it should be understood that electrostaticcollimation without secondary ionization may also be useful. Particlessputtered from the target 16 have some inherent level of ionizationcaused by the sputter process, so the electrostatic collimator 40 willcollimate the sputtered ions even where secondary ionization is notsupplied. However, without the tuned secondary ionizer 32 whichselectively ionizes the target particles without ionizing undesirableparticles, using the electrostatic collimator 40 alone would provide thesame undesirable affects of bombarding the substrate the argon ions, forinstance.

Additionally, the electrostatic collimator 40 may be positioned betweenthe plasma and the secondary ionization zone created by secondaryionizer 32, as demonstrated by the apparatus 54 illustrated in FIG. 7.In this fourth embodiment, ionized target atoms in the plasma areextracted from the region 26 by the physical momentum created by theplasma. The electrostatic collimator 40 is provided with a bias whichsteers and collimates the ions before they recombine to form neutralparticles. Hence, the particles exiting the electrostatic collimator 40are initially collimated as they enter the secondary ionization zonecreated by the secondary ionizer 32. The secondary ionization zone, asin the other embodiments, ionizes or re-ionizes the target particleswhile leaving other particles unaffected. Thus, the re-ionized targetatoms are further laterally accelerated and collimated by the biassupply 30 toward the substrate 12.

FIG. 8 illustrates a fifth embodiment of a sputtering apparatus 50. Asabove, to prevent confusion, elements in FIG. 8 that are analogous toelements in FIG. 1 are identified with identical reference numerals andmay be considered to operate in the manner described above. In the fifthembodiment, collimation is provided by a combination of DC electrostaticfield and a static magnetic field provided by the coils 52. The coils 52are wrapped about the deposition chamber to form a solenoid. A DCcurrent is passed through coils 52 to create a static magnetic fieldhaving field lines longitudinally aligned between the plasma in theregion 26 and the substrate 12. Although a magnetic field cannotinfluence neutral atoms, the addition of the secondary ionizer 32operating through the window 34 selectively ionizes the target particleswithout ionizing other particles within the static magnetic fieldcreated by coils 52. The longitudinal force lines of the static magneticfield apply a longitudinal momentum to the ionized target atoms tocreate a collimated stream between the plasma and the substrate 12,while the neutrally charged argon atoms, for instance, are not affectedby the magnetic field.

A typical semiconductor wafer which may be processed by the apparatusdescribed above is illustrated in FIG. 9 and designated by a referencenumeral 70. The wafer 70 includes a number of different regions, knownas die regions 72. Each die region 72 may include an integrated circuitcontaining various features and fabricated using various materials andprocesses. For the purposes of this discussion, one of the die regions72 will be discussed.

The die region 72 includes a thin titanium-containing film. An exampleof such a film is illustrated in FIG. 10. Specifically, FIG. 10illustrates a cross-sectional view of the die region 72 which includesan enhanced doped region or active region 74 within a semiconductorsubstrate 76. The active region 74 by be formed by an implantationprocess, for instance. The bulk substrate 76 is coated with aninsulative layer 78, such as borophosphosilicate glass (BPSG) orphosphosilicate glass (PSG). The insulative layer 78 is etched to form acontact opening 80 through the insulative layer 78 to the active region74. Of course it should be understood that the depiction of a contactopening to an active region is merely exemplary of a high-aspect ratiofeature and that this discussion applies to other high-aspect ratiofeatures, such as trenches and vias, as well.

Using the methods and apparatus described in detail above, a layer oftitanium or titanium-containing film 82 is deposited across the wafersuch that it covers the bottom of the contact opening 80. It should benoted that little of the film 82 is deposited on the sidewalls of thecontact opening 80 due to the excellent directionality imparted to thetarget particles by the apparatus described above. Furthermore, itshould be noted that the die region 72 has not been damaged bybombardment of undesirable argon ions due to the selectivity of thesecondary ionizer 32 described above.

The thin film 82 advantageously exhibits good adhesion to the contactopening 80 and the active region 74, along with good adhesion to asubsequently deposited conductive metal layer 84 illustrated in FIGS. 11and 12. The metal layer 84 may be titanium, for example, which isdeposited in essentially the same manner as the thin film 82. Of course,the manner in which the selectivity of the secondary ionizer 32 is tunedmay differ due to differences in particulate composition between thethin film 82 and the metal layer 84. As illustrated by the partiallyfilled contact opening 80 in FIG. 11, little of the metal layer 84 isdeposited on the sidewalls of the contact opening 80 due to theexcellent directionality imparted to the target particles by theapparatus described above. Thus, as illustrated in FIG. 12, the metallayer 84 may completely fill the contact opening 80 without the creationof undesirable voids or seams.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the invention is not intended to be limitedto the particular forms disclosed. Rather, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the following appended claims.

1. An apparatus for depositing film on a substrate, the apparatus comprising: a deposition chamber adapted to hold target particles and other particles; an ionizer adapted to create an ionization zone to selectively ionize the target particles passing through the ionization zone while leaving the other particles passing through the ionization zone substantially unaffected; and an electrostatic collimator adapted to electrically steer the ionized target particles through the electrostatic collimator and toward the substrate.
 2. The apparatus, as set forth in claim 1, wherein the deposition chamber comprises a support for holding a source of the target particles.
 3. The apparatus, as set forth in claim 1, wherein the deposition chamber comprises a support for holding the substrate.
 4. The apparatus, as set forth in claim 3, wherein the substrate comprises a semiconductor wafer.
 5. The apparatus, as set forth in claim 1, comprising: a plasma generator creating a plasma within the deposition chamber to initially ionize the target particles.
 6. The apparatus, as set forth in claim 5, wherein the ionization zone is separated from the plasma by a recombination zone in which the initially ionized target particles de-ionize prior to being re-ionized in the ionization zone.
 7. The apparatus, as set forth in claim 1, wherein the ionizer comprises a laser having a wavelength and power chosen to ionize the target particles in preference to the other particles.
 8. The apparatus, as set forth in claim 7, wherein the laser comprises one of an excimer laser and an EUV laser.
 9. The apparatus, as set forth in claim 1, wherein the target particles comprise titanium-containing particles.
 10. The apparatus, as set forth in claim 1, comprising: a static field generator creating an static field within the deposition chamber to accelerate the ionized target particles along a given trajectory toward the substrate.
 11. The apparatus, as set forth in claim 1, wherein the deposition chamber comprises a mirrored inner surface.
 12. The apparatus, as set forth in claim 11, wherein the ionizer comprises a laser arranged to direct optical energy onto the mirrored inner surface of the deposition chamber, the mirrored inner surface creating a plane of optical energy.
 13. The apparatus, as set forth in claim 1, wherein the ionizer comprises a plasma generator.
 14. The apparatus, as set forth in claim 1, wherein the ionizer comprises a microwave generator.
 15. The apparatus, as set forth in claim 1, wherein the target particles comprise a refractory metal.
 16. The apparatus, as set forth in claim 1, comprising at least one secondary ionizer adapted to create at least one secondary ionization zone, the at least one secondary ionizer adapted to promote ionization of the target particles as the target particles pass through the at least one secondary ionization zone while leaving the other particles substantially unaffected as the other particles pass through the at least one secondary ionization zone.
 17. The apparatus, as set forth in claim 1, wherein the electrostatic collimator comprises: a first conductive grid; a first DC voltage source having a polarity matching that of the ionized target particles coupled to the first conductive grid; a second conductive grid placed adjacent the first conductive grid; and a second DC voltage source having a polarity opposite that of the ionized target particles coupled to the second conductive grid.
 18. An apparatus for depositing a film on a substrate, the apparatus comprising: a deposition chamber adapted to contain inert particles, target particles, and a substrate, wherein the target particles comprise titanium-containing particles; a plurality of ionizers creating a plurality of ionization zones within the deposition chamber, each of the plurality of ionizers ionizing the target particles as they pass through each of the respective ionization zones while leaving the inert particles substantially unaffected; and a field generator creating a field within the deposition chamber to accelerate the ionized target particles generally along a given trajectory to the substrate.
 19. The apparatus, as set forth in claim 18, wherein the deposition chamber comprises a support for holding a source of the target particles.
 20. The apparatus, as set forth in claim 18, wherein the deposition chamber comprises a support for holding the substrate.
 21. The apparatus, as set forth in claim 18, wherein the substrate comprises a semiconductor wafer.
 22. The apparatus, as set forth in claim 18, wherein the deposition chamber comprises a port for entry of the inert particles.
 23. The apparatus, as set forth in claim 18, comprising: a plasma generator creating a plasma within the deposition chamber to initially ionize the target particles.
 24. The apparatus, as set forth in claim 23, wherein the plurality of ionization zones are separated from the plasma by a recombination zone in which the initially ionized target particles de-ionize prior to being re-ionized in the plurality of ionization zones.
 25. The apparatus, as set forth in claim 18, wherein each of the plurality of ionizers comprises: an optical ionizer adapted to create a plane of optical energy within the deposition chamber, the optical energy selectively ionizing the target particles passing through the plane while leaving the inert particles passing through the plane substantially unaffected.
 26. The apparatus, as set forth in claim 18, wherein each of the plurality of ionizers comprises a laser having a wavelength and power chosen to ionize the target particles in preference to the inert particles.
 27. The apparatus, as set forth in claim 26, wherein the laser comprises one of an excimer laser and an EUV laser.
 28. The apparatus, as set forth in claim 18, wherein the target particles comprise a refractory metal.
 29. The apparatus, as set forth in claim 18, wherein the field generator comprises: an electrostatic field generator adapted to create an electrostatic field to accelerate the ionized target particles along a substantially collimated trajectory toward the substrate.
 30. The apparatus, as set forth in claim 18, wherein the field generator comprises: a magnetic field generator adapted to create a magnetic field to accelerate the ionized target particles along a substantially collimated trajectory toward the substrate.
 31. The apparatus, as set forth in claim 18 wherein each of the plurality of ionizers comprises a plasma generator.
 32. The apparatus, as set forth in claim 18, wherein each of the plurality of ionizers comprises a microwave generator.
 33. The apparatus, as set forth in claim 18, comprising an electrostatic collimator adapted to electrically steer the ionized target particles toward the substrate.
 34. The apparatus, as set forth in claim 33, wherein the electrostatic collimator comprises: a first conductive grid; a first DC voltage source having a polarity matching that of the ionized target particles coupled to the first conductive grid; a second conductive grid placed adjacent the first conductive grid; and a second DC voltage source having a polarity opposite that of the ionized target particles coupled to the second conductive grid.
 35. A method of manufacturing an integrate circuit, comprising the acts of: passing target particles and inert particles through at least one ionization zone in a deposition chamber to ionize the target particles while leaving the inert particles substantially unaffected; and steering the ionized target particles into a collimated stream directed along a given path toward the substrate using an electrostatic collimator.
 36. The method, as set forth in claim 35, wherein the act of steering comprises the acts of: using a first grid of the electrostatic collimator to attract the ionized target particles; and using a second grid of the electrostatic collimator to direct the ionized target particles through the electrostatic collimator.
 37. The method, as set forth in claim 35, wherein the act of steering comprises the act of charging the substrate to attract the ionized target particles passing through the electrostatic collimator.
 38. The method, as set forth in claim 35, wherein the act of passing comprises the act of passing target particles comprising a refractory metal through the at least one ionization zone.
 39. The method, as set forth in claim 35, wherein the act of passing comprises the act of passing target particles comprising titanium-containing particles through the at least one ionization zone.
 40. The method, as set forth in claim 35, wherein the act of passing comprises the act of passing the target particles and the inert particles through a plurality of ionization zones. 